The prototype of a 4He pumped vector magnetometer is presented. Large auxiliary coils systems used in previously developed apparatus to allow vector measurements from a scalar (atomic or nuclear resonance) sensor are replaced by a light triaxial modulation system associated with advanced techniques of signal processing. The performances of the helium scalar sensor are first briefly recalled; then the principle of the vector measurement, obtained by adding three (approximately) orthogonal modulations of different frequencies (all of the order of 10 Hz) is explained. Afterwards a second part of the paper is devoted to the calibration process, and a first estimate of the performances of the vector magnetometer is obtained. They confirm that this instrument could be a good candidate for an automatic absolute magnetic observatory: after the calibration process completion and a proper installation, it would provide by itself the absolute value of three orthogonal components of the field. In addition to that, the 4He vector magnetometer appears to be also promising for space applications.